Yeast extract has been used widely as a seasoning comprising natural materials, and yeast extract has characteristics such that it highly safe and has complex taste such as unique flavor and body which artificial seasonings is absent. In recent years, furthermore, yeast extract has been drawing attention as materials for cosmetics and healthy food, wherein useful amino acids and nucleic acids contained in yeast extract are effectively utilized.
However, yeast extract has unique yellow or brown color and characteristic odor, and these work as factors severely limiting the applicable range of yeast extract or the amount thereof to be used.
For the purpose of removing such color or odor, therefore, various proposals have been made conventionally. For example, the proposals are made about deodorizing by means of hydrophobic resins (Japanese Patent Application No. 131064/1992 etc.), deodorizing by means of enzyme treatment, chemical treatment methods by acids or alkalis (Japanese Patent Laid-open No. 11188/1976 etc.), or yeast selection for producing yeast extract (Japanese Patent Laid-open No. 66861/1974). Although the processes of these methods are very laborious, however, the resulting advantages are poor disadvantageously, so the methods are not so frequently carried out currently.
The reason of the coloring of yeast extract lies in that at the process of producing yeast extract, saccharides (carbohydrates) and amino acids cause aminocarbonyl reaction through the heating process, with the resultant production of a substance colored dark brown. Heating treatment is carried out in the course of producing seasonings and cosmetics from a raw material yeast extract, so those nearly colorless at the stage of raw materials might potentially be colored at the intermediate stage of the production methods.